1. Field of the Invention
In the development of light-emitting components for electronic or photonic applications, inorganic semi-conductors such as gallium arsenide are mostly used. Point display elements can be prepared from these types of substances. It is not possible to produce display elements with large areas.
2. Description of the Prior Art
In addition to semiconductor light-emitting diodes, electroluminescent devices based on vapour-deposited low-molecular weight organic compounds are known (U.S. Pat. No. 4,539,507, U.S. Pat. No. 4,769,262, U.S. Pat. No. 5,077,142, EP-A 406 762). Again, only small LEDs can be produced with these materials, as a result of the method of manufacture. In addition, these electroluminescent devices have a high production cost and the vapour-deposited amorphous layer is prone to morphological changes which can cause a reduction in the intensity of electroluminescence and the operating time.
Polymers such as poly-(p-phenylenes) and poly-(p-phenylenevinylenes) are described as electroluminescent: G. Leising et al., Adv. Mater. 4 (1992) no. 1; Friend et al., J. Chem. Soc., Chem. Commun. 1992, p. 32-34; Saito et al., Polymer, 1990, vol. 31, 1137; Friend et al., Physical Review B, vol. 42, no. 18, 11670 or WO 90/13148.
In contrast to fully conjugated polymers, polycondensates which are not fully conjugated and which have luminescent structural units are also described in electroluminescent devices (Macromol. Chem. Phys. 195, 2023-2037 (1994)).
In contrast to other materials, polymeric substances for use in electroluminescent devices are characterised by good mechanical and thermal stability. In addition, the production of large surface area light-emitting elements may be enabled due to the possibility of casting and spin-coating polymeric substances.